Effects of Bethe-Heitler pair production in ultraluminous X-ray sources
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arXiv
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| Auteurs principaux: | , , |
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| Format: | Preprint |
| Publié: |
2025
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| _version_ | 1866911137212137472 |
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| author | Romero, Gustavo Esteban Pasquevich, Lucas Manuel Abaroa, Leandro |
| author_facet | Romero, Gustavo Esteban Pasquevich, Lucas Manuel Abaroa, Leandro |
| contents | Some black holes in X-ray binaries accrete at rates far above the Eddington limit. In this supercritical regime, photons are trapped in a radiation-dominated, geometrically thick disk. The innermost regions form a complex environment of intense radiation, strong magnetic fields, and powerful outflows, where radiation-driven winds expel large amounts of mass. These conditions suppress primary relativistic electrons within the transparent funnel along the black hole's spin axis. We show that high-energy electrons can instead arise as secondary pairs from Bethe-Heitler interactions between relativistic protons and ambient photons. Using self-similar models of accretion disks with strong winds of ultraluminous X-ray sources (ULXs), we compute particle acceleration via magnetic reconnection and diffusive shocks, evaluate energy losses, and assess the efficiency and spectral imprint of Bethe-Heitler pair production. Our results suggest that secondary pairs can yield nonthermal radiation in the 0.1-100 MeV range with luminosities from $10^{34}$ up to $10^{38}$ erg s$^{-1}$. This emission could be detectable by future MeV instruments from Galactic ULXs, offering evidence of relativistic protons in their inner funnels and revealing misaligned, otherwise hidden, super-Eddington sources in the Milky Way. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_03735 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Effects of Bethe-Heitler pair production in ultraluminous X-ray sources Romero, Gustavo Esteban Pasquevich, Lucas Manuel Abaroa, Leandro High Energy Astrophysical Phenomena Some black holes in X-ray binaries accrete at rates far above the Eddington limit. In this supercritical regime, photons are trapped in a radiation-dominated, geometrically thick disk. The innermost regions form a complex environment of intense radiation, strong magnetic fields, and powerful outflows, where radiation-driven winds expel large amounts of mass. These conditions suppress primary relativistic electrons within the transparent funnel along the black hole's spin axis. We show that high-energy electrons can instead arise as secondary pairs from Bethe-Heitler interactions between relativistic protons and ambient photons. Using self-similar models of accretion disks with strong winds of ultraluminous X-ray sources (ULXs), we compute particle acceleration via magnetic reconnection and diffusive shocks, evaluate energy losses, and assess the efficiency and spectral imprint of Bethe-Heitler pair production. Our results suggest that secondary pairs can yield nonthermal radiation in the 0.1-100 MeV range with luminosities from $10^{34}$ up to $10^{38}$ erg s$^{-1}$. This emission could be detectable by future MeV instruments from Galactic ULXs, offering evidence of relativistic protons in their inner funnels and revealing misaligned, otherwise hidden, super-Eddington sources in the Milky Way. |
| title | Effects of Bethe-Heitler pair production in ultraluminous X-ray sources |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2509.03735 |